None of the eight famous translated works by Yan Fu can be classified into the category of complete translation,but that of translation variation can absorb Western academic thoughts faster,better and more economically with the guidance of certain objectives.The causes of Yan Fu''s employing such adaptation strategies during his translating as amplification,omission,edition,narration,condensation,combination,re-writing,and imitation can be grouped into the following aspects:1 .social context,2.concerns for China''s destiny,3.multi-requirements of China''s intellectuals,4.the desire of China''s academic circle,5.strong awareness of combining his knowledge with the spread of Western thoughts,and 6.the Matthew effect with his successful translation of Huxley''s Evolution and Ethics.All of the causes contribute to the great success of Yan Fu''s translation of Western academic thoughts.